There has conventionally been known a pressure accumulating apparatus in which hydraulic pressure generated by a pump (fluid pressure conversion means) driven by a vehicle engine (power source) is accumulated in an accumulator (accumulating means) and the accumulated hydraulic pressure is utilized. It has been known that, in this type of the pressure accumulating apparatus, when the hydraulic pressure accumulated in the accumulator is not more than a predetermined pressure, high-pressure hydraulic fluid discharged from the pump is supplied to the accumulator, while when the hydraulic pressure accumulated in the accumulator exceeds the predetermined pressure, the escape of the hydraulic fluid discharged from the pump to a reservoir through a relief valve is allowed for reducing a load of the pump. (Japanese Unexamined Patent Application No. 9 (1998)-286321)
However, in the aforesaid conventional apparatus, although the load of the pump is relieved when the hydraulic pressure accumulated in the accumulator exceeds the predetermined pressure, the pump is kept driven by the vehicle engine. Accordingly, the components in the pump (e.g., piston) are kept operated. Therefore, this provides insufficient relief in the load, and further, adversely affects the durability of the components in the pump.